python倒三角形每行奇数个_python – 沿着下三角形numpy数组的每一行翻转非零值...

这个怎么样：

# row, column indices of the lower triangle of B

r, c = np.tril_indices_from(B)

# flip the column indices by subtracting them from r, which is equal to the number

# of nonzero elements in each row minus one

B[r, c] = B[r, r - c]

print(repr(B))

# array([[ 1. , 0. , 0. , 0. ],

# [ 0.75, 0.25, 0. , 0. ],

# [ 0.7 , 0.2 , 0.1 , 0. ],

# [ 0.1 , 0.4 , 0.3 , 0.2 ]])

相同的方法将推广到由多个下三角形子矩阵组成的任意N维数组：

# creates a (200, 20, 4, 4) array consisting of tiled copies of B

B2 = np.tile(B[None, None, ...], (200, 20, 1, 1))

print(repr(B2[100, 10]))

# array([[ 1. , 0. , 0. , 0. ],

# [ 0.25, 0.75, 0. , 0. ],

# [ 0.1 , 0.2 , 0.7 , 0. ],

# [ 0.2 , 0.3 , 0.4 , 0.1 ]])

r, c = np.tril_indices_from(B2[0, 0])

B2[:, :, r, c] = B2[:, :, r, r - c]

print(repr(B2[100, 10]))

# array([[ 1. , 0. , 0. , 0. ],

# [ 0.75, 0.25, 0. , 0. ],

# [ 0.7 , 0.2 , 0.1 , 0. ],

# [ 0.1 , 0.4 , 0.3 , 0.2 ]])

对于上三角矩阵,您可以简单地从c中减去r,例如：

r, c = np.triu_indices_from(B.T)

B.T[r, c] = B.T[c - r, c]